Dynamic Host Configuration Protocol (DHCP) allows automatic configuration of client's hosts, and more specifically dynamic assignment of network addresses. DHCP is built on a client-server model, where designated DHCP servers allocate network addresses and deliver configuration parameters to dynamically configured hosts. DHCP assigns network addresses for a finite period of time (referred to as a lease) and re-uses them once they are released, thereby postponing exhaustion of available network addresses.
An access unit provides subscribers with an access towards a data communication network. Examples of an access unit are an access multiplexer or an Ethernet bridge. The access unit typically forwards user traffic at the data link layer (L2). Yet, the access unit may snoop DHCP traffic e.g. for populating an IP anti-spoofing filter (to check whether a network address is validly used by a client).
Network addresses happen to be sometimes duplicated on account of e.g. restart or reboot of the access unit, restart or reboot of the DHCP server, thereby causing communication problems for the corresponding subscribers.
It is an object of the present invention to prevent duplication of network addresses within a data communication system.